1. Field of the Invention
The present invention relates to an improvement of an oil level gauge for measuring the oil level in an oil tank installed in an automobile.
2. Prior Art
Typically, an oil level gauge comprises a rod, a handle and a rubber packing as disclosed in, for example, U.S. Pat. Nos. 3,488,855, 4,941,268, 5,113,594, etc. The rod is ordinarily made of spring steel so that it can be elastically deformed. The handle is made of steel wire or synthetic resin and can be used as a lid for a gauge insertion hole. The packing can be used as the lid for the gauge insertion hole.
In the oil level gauge having such a structure of the various parts, the rod has to be securely connected to the handle when the gauge is inserted into or pulled out of the gauge insertion hole, and water must not enter into the oil tank through the gauge insertion hole. In order to meet these requirements, typically, the rod and the handle are mechanically connected to each other by means of rivets, and the rubber packing is adhered to the rod during baking. Alternatively, a separately-manufactured cup-like lid is attached to the rod and fixedly connected by brazing.
These conventional oil level gauges have various disadvantages such that the assembling of the components is too tedious to manufacture the oil level gauges efficiently and that the oil level gauges are heavy because the spring steel is used. In this connection, it has been thought of to make the rod and the handle of synthetic resin, light metal or the like for the purpose of reducing the weight of the oil level gauge. Also, in order to facilitate the assembling of the components into the oil level gauge, a study has been made of such structure of the oil level gauge that the components can be readily assembled by snap action.
In case of the snap-fitting structure, the components of the oil level gauge are not integrally connected by welding or the like. Thus, it is necessary to satisfy the following requirements: (1) the rod and the handle are engaged with each other by a mechanical strength which is enough to prevent accidental disconnection of the rod from the handle when the oil level gauge is inserted into or extracted from the gauge insertion pipe; and (2) water does not enter into the oil tank through a gap at the joint portion between the rod and the handle. As a method for realizing the above item (1), it is a common measure to make an engagement portion of the rod by rigid snap-fitting claws and to utilize a larger engagement structure. In such conventional methods, problems still remain that an efficiency in assembling work is decreased and that the rod and the handle cannot be formed to have large sizes and necessary shapes for assuring sufficient strength since a space an oil level gauge occupies is restricted.
Meanwhile, there is another factor for accidental disconnection of the handle. That is, the rubber packing sticks to an inner wall of the gauge insertion pipe. As a method for preventing this rubber sticking problem, it has been suggested to make the contacting surface of the rubber packing coarse. However, this method has problems that a packing product is not smoothly detached from the die during molding process and that the rubber debris often adheres on the surface of the die.